I start most of my trees and garden plants from seed. I would rather start them in place from seed outside but we have these creatures called field mice who do not appreciate me growing trees in their field and tend to eat them soon after they germinate. Part of the fencing plan on this farm is to plant hedges in order to eventually replace as much of the fence as possible with a permanent living fence. I therefore need a greenhouse large enough to hold thousands of seedlings per season as a hedge requires a tree every 12-18 inches. I settled on the above design because it is large, relatively inexpensive, and very sturdy compared to a regular pvc or metal hoop house with the hoops spaced a few feet apart. Credit for this design goes to TexasPrepper2 and can be seen HERE.
I built the greenhouse under a nice old box elder in the backyard so I don't need shade cloth. I started with a 2x10 pressure treated box 7' wide by 16'7" long on the ground. I then bowed the 50"x16' cattle panel to form an arch over the box and stapled the bottom of the arch to the frame with fencing staples. When all 4 panels were attached, I tied them together with baling wire.
I then built the end frame for the door on one end and a window on the other end and cut an old garden hose in half to protect the plastic from the sharp edges of the cattle panel. After stretching the plastic on, I brought 3-55 gallon black plastic drums filled with water into it to regulate the temperature. After that I built shelves and put an automatic misting system into it with parts bought on Amazon.
Field mice will not only eat sprouted seedlings, but they will also enter your greenhouse and dig up EVERY SINGLE SEED out of your trays and eat them. Even the ones on shelves 3' off the ground. It is extremely frustrating to come into your greenhouse the day after planting 1000 seed cells and finding them disturbed, dug up, and the seed eaten and the shells strewn all over the place (ask me how I know). I decided to staple and bury a 6" barrier of wire cloth to the base of the greenhouse and run a piece of smooth wire over the plastic to prevent mice or mole or voles from entering the greenhouse and wasting my time. I have had no critters since the installation of these 2 barriers and would highly recommend making sure your greenhouse is critter tight before using it.
This is what it looks like inside after a full season of growing. I have a mix of Osage Orange, Black Locust, Honey Locust, and Mimosa ready to go out. I estimate that I have 2000 trees here on my first try at planting trees from seed in a greenhouse. With further optimization and lessons learned I think I could fit 4000. Ill do more on plant starting in another series of posts.